Hey guys,
Another question for you all experienced with casting...
I plan to build a big foundry, good for 15lbs of aluminum.
The design of my pieces that I will be casting are Snowguns, basically I will be making foam pieces that will be 1/2"diameter, 3/4"diameter, and 3-5" diameter tubes. Basically the small 1/2-3/4" tubes will be inside the 5" tube. Wall thicknesses of the small tubes will be about a regular schedule 80 aluminum pipe, outter walls of the large pipe will be about 1/4" thick. The pieces will be connected by flat 1/4" thick discs. Here's a picture of what it will look like, its just a little bit of it.
farm5.static.flickr.com/4047/4303933514_9c268c8b0d_b.jpg
I need extremely good casting quality, the pipes need to withstand 700+PSI of water. My idea is just to use that 2" thick 4'x8' sheets of high density foam for insulation at lowes as my lost foam. I heard thats good stuff to use. I'll use super 77 spray glue and just cut out the design with that with a foam cutter. I will account for about a 6% shrinkage factor as well. The metal will basically be automotive engine aluminum, high quality stuff.
So for the sand I plan on just using regular sand. Since I need sand inside the actual foam pieces, I don't think I can get any other type of regular sand inside the foam pieces properly.
I've got about 300lbs of regular sand and i'm in the process of sifting it out. I've got a 350micron rated mesh and also a very very fine 150micron mesh. So basically the sand i'm going to have is super fine.
Does that all sound like a good idea? The only thing im concerned with is not compacting the sand enough for the mold. Also, im worried that the aluminum will start to cool before it fully fills the foam. The maximum depth from the top of the casting will be about 12". So basically the aluminum won't travel that far down into the sand. Also I plan to pressure cast. Have one of those pipes of the top above the sand and fill the mold above it with about 5lbs of aluminum so that it pushes down on the mold and fills it completely. Do I need like a vent for the casting? probably not since its in regular sand and also its a pressure cast?
Let me know,
thanks,
Matt
